Fabrication of an amino-terminated organic surface by chemical conversion of a nitro-terminated self-assembled monolayer

Self-assembeld monolayers (SAMs) formed by the adsorption of 4′-nitro-1,1′-biphenyl-4-thiol (NBT) on gold substrates were studied using infrared reflection-absorption spectroscopy (IR-RAS). The IRRAS results revealed that the straightforward approach for the fabrication of SAMs, namely, immersions of the gold film in organothiol solutions, leads to the formation of highly oriented SAMs. To prepare highly oriented amino-terminated SAMs, the nitro-terminated SAMs were immersed into ZnCl₂/HCl solution to chemically convert the nitro group to an amino group. IR spectra recorded for this conversion revealed that the conversion is completed after a fairly short period of time (45 min.), immersion for longer time results in the etching of the SAMs by the acidic solution.